The present invention relates to a method for the register correction of a processing machine, and a related processing machine, a related computer program, and a related computer program product.
Although the text below refers mainly to printing presses, the present invention is not limited thereto, but rather is directed to all types of processing machines with which a continuous material and/or a material web is processed. The present invention may be used, in particular, with printing presses such as newspaper presses, jobbing presses, gravure presses, printing presses for packaging or currency, and processing machines such as bagging machines, envelope machines, or packaging machines. The continuous material may be paper, cardboard, plastic, metal, rubber, or foil, etc.
With the related processing machines, in particular printing presses, a continuous material is moved along by driven axles (web conveyance axles or devices), such as tension rollers or feed rollers, and by non-driven axles, such as breaker rollers, guide rollers, drying rollers, or cooling rollers. The continuous material is simultaneously processed, e.g., it is printed on, punched, cut, folded, etc., using processing axles, which are usually also driven. The driven axles influence the web tension and the processing register, e.g., a color or longitudinal register.
With printing presses, e.g., gravure presses, the longitudinal register is controlled, for instance, in order to obtain an optimal print result. A compensator is often used as the adjusting axle for the register correction. The compensator is a mechanical device located in the continuous material flow upstream of the printing unit that influences the length of the continuous material in the continuous material section upstream of the printing unit.
With color printing presses, in particular with gravure presses, colors must be printed directly one over the other in order to obtain a good printing result. If register deviations occur in the longitudinal register (color register), a register control may typically be carried out using compensators. In this case, the compensator upstream of the printing unit with the register deviation is displaced, which results in a shortening or lengthening of the path of the continuous material, i.e., the length of the continuous material in the particular material section upstream of the printing unit. As a result, the printed image produced by the printing unit is shifted in a stationary manner directly behind the compensator in proportion to the printed images produced by the other printing units.
At the instant when the shift is carried out, the web tension changes only in the web section located upstream of the printing unit with the register deviation. Due to the web conveyance, the change in web tension propagates into the subsequent web sections, which results in a register deviation and activates the register control of the subsequent printing units. Since this register deviation dies out, in principle, once the stationary state is reached, even without being regulated, control strategies are also known with which the register control of the subsequent printing units is deactivated until the deviation dies out.
The known solutions therefore have the disadvantage that the displacement of a compensator for longitudinal register correction is not decoupled. Due to the web conveyance, the difference in web tension propagates into the subsequent web sections, which results in the register control of the subsequent printing units being triggered, and/or it results in waste.